A Long Non-Coding RNA of Citrus tristeza virus: Role in the Virus Interplay with the Host Immunity.

During infection, Citrus tristeza virus (CTV) produces a non-coding subgenomic RNA referred to as low-molecular-weight tristeza 1 (LMT1), which for a long time has been considered as a by-product of the complex CTV replication machinery. In this study, we investigated the role of LMT1 in the virus infection cycle using a CTV variant that does not produce LMT1 (CTV-LMT1d). We showed that lack of LMT1 did not halt virus ability to replicate or form proper virions. However, the mutant virus demonstrated significantly reduced invasiveness and systemic spread in Nicotiana benthamiana as well as an inability to establish infection in citrus. Introduction of CTV-LMT1d into the herbaceous host resulted in elevation of the levels of salicylic acid (SA) and SA-responsive pathogenesis-related genes beyond those upon inoculation with wild-type (WT) virus (CTV-WT). Further analysis showed that the LMT1 RNA produced by CTV-WT or via ectopic expression in the N. benthamiana leaves suppressed SA accumulation and up-regulated an alternative oxidase gene, which appeared to mitigate the accumulation of reactive oxygen species. To the best of our knowledge, this is the first report of a plant viral long non-coding RNA being involved in counter-acting host response by subverting the SA-mediated plant defense.

Isolation and structural characterization of a non-diketopiperazine phytotoxin from a potato pathogenic Streptomyces strain.

Two Streptomyces spp. strains responsible for potato common scab infections in Uruguay which do not produce diketopiperazines were identified through whole-genome sequencing, and the virulence factor produced by one of them was isolated and characterized. Phylogenetic analysis showed that both pathogenic strains can be identified as S. niveiscabiei, and the structure of the phytotoxin was elucidated as that of the polyketide desmethylmensacarcin using MS and NMR methods. The metabolite is produced in yields of ∼200 mg/L of culture media, induces deep necrotic lesions on potato tubers, stuns root and shoot growth in radish seedlings, and is comparatively more aggressive than thaxtomin A. This is the first time that desmethylmensacarcin, a member of a class of compounds known for their antitumor and antibiotic activity, is associated with phytotoxicity. More importantly, it represents the discovery of a new virulence factor related to potato common scab, an economically-important disease affecting potato production worldwide.

Determinación de factores de virulencia asociados a Escherichia Coli Enterohemorrágica en cepas peruanas aisladas entre 1999-2001 / Determination of virulence factors related to Escherichia Coli enterohemorragic Peruvian strain isolated between 1999-2001

En el presente estudio se intentó detectar la presencia del gen de toxina en cepas locales de Escherichia Coli serológicamente relacionados a la catergoria enterohemorrágica, caracterizando además un aislamiento reportado como serotipo 0157:H7 procedente de la ciudad de Tacna (cepa Tacna 410), mediante la reacción en cadena de la polimerasa (PCR) y secuenciamiento. Los resultados confirmaron la presencia del gen de la toxina shiga sólo en la cepa Tacna 410, obteniéndose una identidad del 100 por ciento entre la secuencia nucleótida del gen de la copa Tacna 410 y secuencias reportadas de la toxna shiga de tipo II en el Genebank. Asimismo, se detectó en la cepa Tacna 410 propiedades hemolíticas y el gen eae asociado al fenómeno de attaching and effacing, características de una típica cepa de ECEH.

We tried to detect the Shiga gene in local Escherichia Coli strains serologically related the enterohemorragic category. At the same time, using polymerase chain reaction (PCR) and sequencing, we characterized a strain confirmed as E. Coli 0157:H7 serotype, which was isolated in Tacna (a city in southern Peru) (Tacna 410 strain). Our results confirmed the presence of the Shiga toxin gene only in E. coli strain Tacna 410, and we found 100 percentage identify between the sequence from the amplified gene and reference sequence for type II Shiga toxin in the gene bank. We also detected in the Tacna 410 strain hemolytic properties and the eae gene, which is associated to attaching and effacing lesions, typical features of EHEC, strains.